1. 1 Abstract - KNU and KIGAM are developing a ground-based Arc-scanning SAR system (ArcSAR) mounted on a truck. The system achieves a coherent integration of radar returns from ground targets by the circular motion of the antennae attached to the end of an extendable arm. Precise control of antenna position and the extended coherent-integration-length enable the formation of high-resolution, high- precision and phase-preserving SAR images. Deramp-FFT algorithm was used for ArcSAR Spot Mode focusing while Range-Doppler algorithm was implemented for ArcSAR Scan Mode, both in polar format. ArcSAR Spot Mode has 3.14 times higher resolution than GB-SAR, while ArcSAR Scan Mode can obtain omnidirectional image with reduced resolution but still has 11 times higher resolution than a conventional real aperture radar. A Ground-Based Arc-Scanning Synthetic Aperture Radar (ArcSAR) System and Focusing Algorithms Hoonyol Lee Department of Geophysics, Kangwon National University, Chuncheon, Republic of Korea (hoonyol@kangwon.ac.kr) Seong-Jun Cho and Kwang-Eun Kim Korea Institute of Geosciences and Mineral Resources, Daejeon, Republic of Korea (mac, kimke@kigam.re.kr)

2. 2 GB-SAR DInSAR tested: Phase stability of 1° (0.1mm range) was achieved for several hours for stable reflectors, rendering phase change of 10 ° to be assured (1mm accuracy). PSInSAR displacement measurement: R 2 =0.9999 achieved. GB-SAR can be used for various applications such as: Safety monitoring of natural or anthropogenic structures Microwave backscattering properties of target New SAR system concept design

3. 3 ArcSAR System

4. 4 ArcSAR Imaging Modes Spot Mode  Dual rotational motion (boom and antenna)  Coherent Integration Arc can be 180 degree maximum.  High resolution  Limited azimuth coverage Scan Mode  Single rotational motion (boom only)  Coherent Integration Arc is the width of the antenna beam.  Low resolution  Full azimuth coverage

5. 5 Deramp Function: Azimuth Compression: IFFT Focused Image: Azimuth (angular) Resolution: Phase: ArcSAR Focusing SPOT Mode : Deramp-FFT Algorithm Deramp-FFT Algorithm in Polar Format Range Compressed Signal: Coherent Integration Arc: Range Function: Taylor’s Expansion at :

6. 6 Range-Doppler Algorithm in Polar Format Range Compressed signal: Coherent Integration Arc: Range Function: Taylor’s Expansion at : Matched Filter: Azimuth Compression: Matched Filtering Focused Image: Azimuth (angular) Resolution: Phase: ArcSAR Focusing SCAN Mode : Range-Doppler Algorithm

7. 7 ArcSAR Focusing Flowchart Raw Data Range Hamming Filter Range Compression Range Migration Azimuth FFT Multiply Deramp function Azimuth Hamming Filter Azimuth FFT Range Migration Azimuth Matched Filter Azimuth Hamming Filter Azimuth iFFT Geometric Correction Output Geometric Correction Output SPOT: Deramp-FFTSCAN: Range-Doppler

8. 8 Azimuth Resolutions

9. 9 Simulation: ArcSAR Spot Mode

10. 10 Simulation: ArcSAR Scan Mode

11. 11 ArcSAR Scan Mode Experiment

12. 12 Conclusions A novel ArcSAR system is developed and mounted on a truck. Deramp-FFT algorithm was used for the ArcSAR Spot Mode. Range-Doppler algorithm was implemented for the ArcSAR Scan Mode. Comparisons of image resolutions between various ground-based radar systems confirmed the advantages of ArcSAR: ArcSAR Spot Mode > Linear-scanning GBSAR > ArcSAR Scan Mode > ArcRAR 167.2 53.4 11.0 1 ArcSAR Spot Mode has 3.14 times higher resolution than GB-SAR. ArcSAR Scan Mode can obtain omnidirectional image with reduced resolution, but still has 11 times higher resolution than a conventional real aperture radar. The system will provide a rapid response tool for various applications such as regional mapping and environmental hazard monitoring.